Personally, I play halo for the community fun (Live AND Local), the campaign, and swat.
Warzone was a mixed ripoff of Battlefield conquest and Invasion.... with a healthy helping of sit and camp, or flinging yourself at the campers - the only difference is the occasional AI. And I've never had to work so hard in a halo game to get my hands on a dmr.
And I agree, the mechanics of the game are smooth, the servers load super fast, everything looks crisp, and I can get into my buddies lobbies (unlike mcc). However, I have much higher expectations than just a game that runs well. I've never see a new game take away so many of the features that we've come to expect in previous titles.
They've missed so many of the things we've all come to love, or things that made halo... different than everyone else. Infection, ctf, koth, oddball, headhunter, etc, etc. and sadly, in its place wasn't even a consolation prize, but a game type with three maps, an arena with only slayer modes, a weird (and still broken for me personally) file share, a late forge, broken theater, and an overall map list that's fairly short, at least when considering all the other features that weren't included.
It comes down to this - halo moving from community/casual focus, to a competitive, online, "one player" mindset. And that's just how it is... I'm not screaming and shouting, just sad. I think others see it, and the sales have reflected it... I don't want a halo that is in the same category as battlefield, titanfall, evolve, cod or destiny. I want something different and better, in all regards.